Not applicable.
1. Field of the Invention
This invention is in the area of fasteners which are molded into foam objects such as a seat bun, specifically a fastener strip with vent holes through the base layer, underneath the fastening elements, to prevent air from being trapped beneath the fastener strip when it is placed on the mold.
2. Description of the Related Art
In a molding process in which a fastener strip is molded into a foam object such as an automobile seat bun, the fastener strip is placed fastening element side-down onto a surface of the mold cavity. Typically, the fastener strip includes side and end sealing means, so that when liquid resin is poured into the mold, the resin does not penetrate underneath the edges of the fastener strip and foul the fastening elements during the foaming process.
However, a problem arises when air is trapped underneath the fastener strip after it has been placed on the mold. The pressure of liquid resin on the top (face-up) surface of the fastener strip, and the pressure generated by the foaming process itself, can cause any air trapped underneath the fastener strip to be forced out under the edges of the fastener stripxe2x80x94that is, through the interface between the mold surface and the fastener strip edges. The escaping air causes voids to form in the foam seat bun around the area of the fastener strip, and thus prevents the seat bun from fully and properly forming. In addition, when the edges of the fastener strip are lifted up by the escaping trapped air, liquid resin can penetrate under the edges and foul the engaging elements of the fastener strip. It can thus be appreciates that a means to relieve the trapped air and prevent the lifting up of the fastener strip edges would be desirable.
A few fastener strips with apertures are shown in the prior art; however, none of these prior art fastener strips contain the structure necessary to vent the fastener strip in a foam molding process.
U.S. Pat. No. 5,061,540 to Cripps et al. shows base layer openings at the outer side edges of a fastener strip. However, these holes are not for venting air from beneath the fastener strip in the molding process. Instead, they allow foam penetration through the outer side edges, and increase the anchoring strength of the side edges within the foam seat bun. Accordingly, Cripps"" holes are not through the portion of the base underneath the fastening elements, as in the invention, and thus cannot achieve the desired venting objective.
U.S. Appl. Pub. #2002/0000488 to Shepard et al. describes a roll of hook fastener strip material with oval cuts, longitudinal slits, and transverse perforations through the base layer, in order to allow a desired length of fastener strip to be torn off the roll. These openings do not have a shape suitable for venting the fastener strip, nor are they spaced properly down the length of the fastener strip to allow for complete and consistent venting, as in the invention. More importantly, Shepard""s device lacks the additional structure needed for use in a foam molding process, e.g. holding means to secure the fastener strip to the mold, and side and end sealing means to prevent foam intrusion from fouling the fastener elements during molding. Finally, with respect to the process for making the fastener strip, Shepard""s openings are not formed in the extruding step as in the invention. Instead, they are cut into the strip after it is molded, using a cutting die, stamp, or similar tool, thus necessitating an extra step in the production process.
U.S. Pat. No. 6,363,587 to Richter similarly shows a roll of fastener strip composite material with perforations through the base layer. However, the perforations on the roll are not for venting the fastener strip during a molding process, but rather for allowing separate individual composite fastener strip structures to be separated from the roll. Following separation of each individual composite fastener strip structure, the perforations form side edges of the fastener strip element, and no longer define venting perforations through the base layer under the fastening elements, as in the invention. Finally, Richter""s device also lacks the additional structure needed for use in a foam molding process, e.g. holding means to secure the fastener strip to the mold, and side and end sealing means to prevent foam intrusion from fouling the fastener elements during molding.
U.S. Pat. No. 5,852,855 to Mody et al. shows a woven hook fastener strip wherein tiny, irregular weave spaces exist between the warp and weft yarns. However, the spaces between the yarns are not suitable for venting the fastener strip in a foam molding application and so not surprisingly, Mody""s device lacks the additional structure needed for use in a foam molding process, e.g. holding means to secure the fastener strip to the mold, and side and end sealing means to prevent foam intrusion from fouling the fastener elements during molding. Further, a thermoplastic base layer is present on the back side of Mody""s device, to bind the yarns together and provide a measure of stiffness. Mody""s thermoplastic base layer does not have through-holes in it, as in the invention.
U.S. Pat. No. 5,997,981 to McCormack et al. describes a fastener strip with a breathable base layer, for use in disposable diapers. The breathable base layer has microscopic openings which allow air to pass through over time, but these openings are much too small to quickly vent a fastener strip in a foam molding process. Further, McCormack""s device also lacks the additional structure needed for use in a foam molding process, e.g. holding means to secure the fastener strip to the mold, and side and end sealing means to prevent foam intrusion from fouling the fastener elements during molding.
Thus it can be seen that a fastener suitable for use in a foam object molding process and which has venting means that prevent air from being trapped under the fastener during the molding process, would be a significant advantage over the prior art.
Accordingly, several objects and advantages of the invention are:
The vent holes improve performance by preventing trapped air from lifting up the edges of the fastener strip during the molding process, thus avoiding fouling of the fastening elements and the creation of voids in the foam seat bun.
In fastener strips employing magnetic or other holding means to secure the fastener strip in position on the mold surface, the lifting up of the edges of the fastener strip also tends to weaken the holding force, thereby making it easier for the fastener strip to inadvertently move from the desired position. The vent holes of the invention allows the holding means to remain securely against the mold surface, thus preventing any inadvertent movement.
The invention can be extruded in just one piece at low cost, without the need for additional manufacturing steps.
Further objects and advantages of the invention will become apparent from a consideration of the drawings and ensuing description.
The invention is a fastener strip with vent holes through the base layer, underneath the fastening elements, to prevent air from being trapped beneath the fastener strip when it is placed on a mold in a foam object molding process.